Currently, various switching elements configured by MEMS elements have been designed. As disclosed in Patent Document 1, for example, some of these switching elements use a piezoelectric actuator.
In the switching element based on a piezoelectric actuator disclosed in Patent Document 1, a cantilever arm is attached to the surface of a base substrate. The arm includes a vertical wall portion serving as a cantilever support portion and having a wall surface orthogonal to the base substrate, and a horizontal wall portion supported by the vertical wall portion and having a wall surface parallel to the base substrate. A movable electrode is formed on the horizontal wall portion. Above the movable electrode, a fixed electrode is formed on the inner wall of a cover portion that covers the arm.
A lower electrode, a piezoelectric film, and an upper electrode are arranged in this order near the support side end of the horizontal wall portion of the arm. These components constitute a piezoelectric drive portion. When a drive voltage is applied between the lower electrode and upper electrode of the piezoelectric drive portion, the piezoelectric film is distorted, the arm bends upwards, and the movable electrode comes into close proximity to the fixed electrode. In this way, as the distance between the movable electrode and the fixed electrode varies depending on whether or not a drive voltage is applied, the switching element functions as a switch or a variable capacitance element.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2009-238546